Freedman, Alan, author
Amacom, 1995
Buku Referensi
Watt, Alec, author
Longman, 1982
Buku Referensi
Hall, James, author
John Murray, 1995
Buku Referensi
Spencer, Donald D.
Camelot Publishing Company, 1993
Buku Referensi
Koren, Herman, author
Lewis Publishers, 1996
Buku Referensi